Interface states at ultrathin oxide/Si(111) interfaces obtained from x-ray photoelectron spectroscopy measurements under biases

The energy distribution of interface states for Si(111)-based metal-oxide-semiconductor (MOS) devices with an ultrathin chemical oxide layer is obtained from measurements of x-ray photoelectron spectra under biases. All the observed interface states have discrete energy levels. The energy deviation of the interface state levels from the midgap is smaller than that for the Si(100)-based MOS devices; this is attributed to weaker interaction of the Si dangling bond with Si and oxygen atoms in the oxide layer. The densities of the interface states at the Si(111)/ultrathin oxide interface are comparable to those at the Si(100)/ultrathin oxide interface.